What does it mean for something to be “natural”? The concept is all over the place. As branding it is something to aspire to. A state that must be protected. Something distinct from humans.

It’s especially jarring in discussions of nutrition and health. The absence of chemicals is ipso facto better for you. The diets of generations past something sacrosanct.

But it’s often an arbitrary distinction.

These orange carrots may not have been sprayed or grown with chemicals, but they’ve been altered by generations of farming. This slice of land may not have any obvious human alterations, no buildings or roads. But our presence in and around it has changed it. We’ve thinned it with our steps and diets. We’ve changed the climate, macro and micro.

Our perceptions of nature are almost always skin deep. Our recognised impact only the most brutal. I’m halfway through a Quarterly Essay on the Murray-Darling Basin, where much of Australia’s agriculture is located and water politics is fierce.

But right now I’m gripped by a contested state of nature:

These stories of the river are increasingly contested, as the engineers attempt to model and restore some portion of “natural” flows. The irrigators on the Lachlan, in their interviews with me, posed the question of what the Water Holder thought the “natural” state of the Cumbung Swamp would have been, and what “sustainable” might look like. What is natural? What people remember from their childhood, what the traditional owners have recorded in stories, or what the water engineers’ models tell us would once have happened before we built dams and locks and weirs and drew away so much of the water for our own use? And how to account for climate change?

The natural state lies outside living memory, in the realm of dreaming and anecdote. In both the real and the political landscape of the Murray–Darling Basin, nature is often referred to, used as a justification for action, but increasingly it is out of reach, a concept rather than a reality.

Put aside that natural appears to be conflated with “healthy”. It’s temporal.

The question seems to be about the baseline. At what point was the river system “natural”? And, if we pick a time when humans were present, why is it any more natural than it is now?